In this SERCA proposal, the principal investigator, a biostatistician, will work with an established team of researchers in epidemiology, occupational medicine, and industrial hygiene, to develop and refine study methods to deal with selection biases that have severely limited our ability to accurately study asthma in the workplace. A previous cross-sectional study of metalworking fluids (MWF) and asthma suffered from well documented biases due to the healthy worker effect (HWE) and sparse information about the pattern of asthma since employment. However, the MWF-asthma link is well enough established by clinical evidence to merit further examination of the exposure-response relationship. To address shortcomings in the earlier study, the cross-sectional sample will be expanded by adding previously excluded females, additional blacks, and new hires to from a new cohort of 3000 autoworkers; and time specific information about asthmatic events - both initial onset of disease as well as exacerbation - will be collected by a mailed questionnaire. The analysis will account for job transfer bias by using time windows to redefine exposure in a more biologically relevant manner and will apply a Cox proportional hazards model to estimate risk in both the cross-section and the cohort. The new methods developed for data collection and analysis will provide the research experience necessary to establish the investigator's career in the occupational health field, improve techniques for studying asthma in cross-sectional studies of working populations, and further our understanding of the relationship between asthma and MWF.